potterton suprima 40

[suluki]

Im having trouble with this boiler as in that when calling for heat and hot water the fan and pump work ok but no spark at the burner then the boiler trips out.
Looking at the pcb i see burn marks on it and assume it is knacked as this is a common fault on these boilers.
if i wanted to test the air flow switch how do i do this, could some one tell me in detail how to carry out this test.

thanks in advance.

 

[MANDATE]

I take you mean 'air pressure switch'
If you look through my past postings you will find the detail you want.
basically fan operates a diaphram which operates a micro switch.With fan operated by a independent electric supply you can check for continuity across the leads from the micro switch.Make sure temporary live replaces permanent live on the fan otherwise fan will rotate wrong way .
I do believe I have detailed this on more than one occasion so suggest you look at them all.